Can Mellobloom be used as a breaker?

Freeing a slot matters because Break is the largest single damage multiplier in the game. Empty an enemy's break bar and it is stunned, taking greatly increased damage until the bar refills. Against bosses that is 250% more. A team that never breaks is giving up its biggest damage window, and Mellobloom lets you have that window without spending a slot on a creature whose only job is to empty the bar.

In practice she fills both jobs at once. She buffs the team, and her hits wear down the break shield under the enemy's health bar. The slot that would have gone to a breaker can go to more damage or another role you are short on.

To speed her up, pair her with Rookie. Its Bouncy Sling makes the targets it hits take 15% more break damage for 15 seconds, and that applies to Mellobloom's hits too.

When a dedicated breaker still makes sense

Mellobloom is a buffer that breaks well. She does not replace the creatures built around breaking. Inferlupa holds the Break combat role and is one of the best breakers, including in dark and Irisalis teams. Magma Rex empties break bars quickly even against enemies that are neutral to its element. Minespine deals 20% extra break damage while tunneling. If your team relies on getting bosses into that stun as often as possible, one of these alongside Mellobloom will open more windows than she can open alone.

Not settled: The exact Break figure is not pinned down. It sits around 204 to 212, so use the range as a guide rather than a precise number.